@@ -733,7 +733,7 @@ const __as_dbGroupBy     = (h, sql, params) => String(globalThis.__as_sqlite.gro
 const __as_dbGroupCount  = (h, table, keyCol) => String(globalThis.__as_sqlite.groupCount(h, table, keyCol));
 // ---- Dom (#56 PR 4): Window / Document / utility ----
 // Host is `globalThis.window` when present (browser, jsdom, idaptik
-// WebView); otherwise `globalThis` so a Deno/Node harness can install
+// WebView); otherwise `globalThis` so a Node/Bun harness can install
 // document/window mocks on the global. No consumer-side init required
 // beyond providing those web-platform objects.
 const __as_domWin = () =>
 
@@ -1,14 +1,22 @@
 // SPDX-License-Identifier: MPL-2.0
-// issue #122 follow-up — Node-ESM harness for new Deno-scripting externs.
+// issue #122 follow-up — Node-ESM harness for the Deno-era scripting externs,
+// now exercised through the Bun-ESM backend.
 //
-// Stubs only what the new surface needs: a tiny in-memory FS for
-// `Deno.readDirSync` (so `walkRecursive` traverses it deterministically),
-// `Deno.args` / `Deno.exit`, and captures `console.error`.
+// Stubs only what the surface needs: a tiny in-memory FS (so `walkRecursive`
+// traverses it deterministically), `args`, `exit`, and captures
+// `console.error`.
+//
+// IMPORTANT: this corpus is compiled with `--bun-esm`, and the emitted Bun
+// prelude resolves `node:fs` lazily via `process.getBuiltinModule()` and reads
+// `process.argv` / `process.exit`. Stubbing a `globalThis.Deno` object is
+// inert under that backend, so the host is stubbed at the seam the emission
+// actually uses.
 
 import assert from "node:assert/strict";
 
 // ── In-memory FS stub for walkRecursive ─────────────────────────────
-// Shape: { "/root": ["a", "b/", ".hidden"], "/root/b": ["c"] }
+// Shape: { "/root": ["a.txt", "sub/"], "/root/sub": ["b.txt", "deeper/"],
+//          "/root/sub/deeper": ["c.txt"], "/empty": [] }
 const fs = {
   "/root":   [{ name: "a.txt",  isFile: true,  isDirectory: false },
               { name: "sub",    isFile: false, isDirectory: true  }],
@@ -18,17 +26,46 @@ const fs = {
   "/empty": [],
 };
 
-globalThis.Deno = globalThis.Deno || {};
-globalThis.Deno.readDirSync = (path) => {
-  const entries = fs[path];
-  if (!entries) throw new Error(`stub: no such dir ${path}`);
-  return entries;
+const fsStub = {
+  readdirSync: (path) => {
+    const entries = fs[path];
+    if (!entries) {
+      const err = new Error(`stub: no such dir ${path}`);
+      err.code = "ENOENT";
+      throw err;
+    }
+    return entries.map((e) => ({
+      name: e.name,
+      isFile: () => e.isFile,
+      isDirectory: () => e.isDirectory,
+    }));
+  },
+  mkdirSync: () => {},
+  writeFileSync: () => {},
+  rmSync: () => {},
+  readFileSync: () => new Uint8Array(),
+  statSync: (path) => {
+    const err = new Error(`stub: no such path ${path}`);
+    err.code = "ENOENT";
+    throw err;
+  },
+};
+
+const realGetBuiltinModule = process.getBuiltinModule?.bind(process);
+process.getBuiltinModule = (name) => {
+  if (name === "node:fs") return fsStub;
+  if (!realGetBuiltinModule) {
+    throw new Error(`host builtin unavailable: ${name}`);
+  }
+  return realGetBuiltinModule(name);
 };
 
 // args / exit stubs — exit captures the code instead of terminating.
+// `args` lowers to process.argv.slice(2), so the leading entries are dropped.
+const realArgv = process.argv;
+process.argv = ["node", "deno_scripting.harness.mjs", "alpha", "beta", "gamma"];
 let lastExit = null;
-globalThis.Deno.args = ["alpha", "beta", "gamma"];
-globalThis.Deno.exit = (code) => { lastExit = code; return code; };
+process.exit = (code) => { lastExit = code; };
 
 // Capture stderr writes from consoleError.
 const stderrLog = [];
@@ -71,4 +108,5 @@ exit_with(2);
 assert.equal(lastExit, 2, "Deno.exit lowered correctly");
 
 console.error = origError;
+process.argv = realArgv;
 console.log("deno_scripting.harness.mjs OK");
@@ -1,7 +1,12 @@
 // SPDX-License-Identifier: MPL-2.0
 // campaign #239 STEP 3 part 2 — Node-ESM harness for the second wave
-// of Deno-scripting externs (stat predicates, byte accessors, module URL)
-// plus the `let _ = X` wildcard-binding codegen fix.
+// of Deno-era scripting externs (stat predicates, byte accessors, module URL)
+// plus the `let _ = X` wildcard-binding codegen fix, exercised through the
+// Bun-ESM backend.
+//
+// The Bun prelude reaches the filesystem through process.getBuiltinModule(),
+// so the in-memory FS is installed at that seam — a `globalThis.Deno` stub
+// would never be consulted.
 
 import assert from "node:assert/strict";
 
@@ -12,24 +17,38 @@ const files = {
   "/empty.bin":         { kind: "file",   bytes: new Uint8Array() },
 };
 
-globalThis.Deno = globalThis.Deno || {};
-globalThis.Deno.statSync = (path) => {
-  const e = files[path];
-  if (!e) {
-    const err = new Error(`stub: no such path ${path}`);
-    err.code = "ENOENT";
-    throw err;
-  }
-  return {
-    size: e.kind === "file" ? e.bytes.length : 0,
-    isFile: e.kind === "file",
-    isDirectory: e.kind === "dir",
-  };
+const fsStub = {
+  statSync: (path) => {
+    const e = files[path];
+    if (!e) {
+      const err = new Error(`stub: no such path ${path}`);
+      err.code = "ENOENT";
+      throw err;
+    }
+    return {
+      size: e.kind === "file" ? e.bytes.length : 0,
+      isFile: () => e.kind === "file",
+      isDirectory: () => e.kind === "dir",
+    };
+  },
+  readFileSync: (path) => {
+    const e = files[path];
+    if (!e || e.kind !== "file") {
+      const err = new Error(`stub: not a file ${path}`);
+      err.code = "ENOENT";
+      throw err;
+    }
+    return e.bytes;
+  },
 };
-globalThis.Deno.readFileSync = (path) => {
-  const e = files[path];
-  if (!e || e.kind !== "file") throw new Error(`stub: not a file ${path}`);
-  return e.bytes;
+
+const realGetBuiltinModule = process.getBuiltinModule?.bind(process);
+process.getBuiltinModule = (name) => {
+  if (name === "node:fs") return fsStub;
+  if (!realGetBuiltinModule) {
+    throw new Error(`host builtin unavailable: ${name}`);
+  }
+  return realGetBuiltinModule(name);
 };
 
 const {
 
@@ -1,7 +1,11 @@
 #!/usr/bin/env bash
 # SPDX-License-Identifier: MPL-2.0
 # Issue #734 — native Bun-ESM backend acceptance runner.
-set -euo pipefail
+#
+# Fail-late by design: every check runs and is reported, so one red check
+# cannot hide the state of the checks behind it. Failures are echoed as
+# `::error::` lines so they survive into CI annotations.
+set -uo pipefail
 
 ROOT_DIR="$(cd "$(dirname "$0")/.." && pwd)"
 TEST_DIR="$ROOT_DIR/tests/codegen-bun"
@@ -14,48 +18,88 @@ else
   COMPILE_CMD=(dune exec affinescript -- compile)
 fi
 
-command -v bun >/dev/null 2>&1 || {
-  echo "error: Bun is required for the Bun-ESM acceptance tests" >&2
+if ! command -v bun >/dev/null 2>&1; then
+  echo "::error::Bun is required for the Bun-ESM acceptance tests" >&2
   exit 1
+fi
+
+failures=()
+fail() {
+  failures+=("$1")
+  echo "::error::$1" >&2
 }
 
 src="$TEST_DIR/host_profile.affine"
 out="${src%.affine}.bun.js"
-"${COMPILE_CMD[@]}" "$src" -o "$out" --bun-esm
-if grep -qi 'deno' "$out"; then
-  echo "error: legacy runtime reference emitted in $(basename "$out")" >&2
-  exit 1
+
+# 1. Compile, then scan the artefact for legacy runtime references.
+compiled=1
+if ! "${COMPILE_CMD[@]}" "$src" -o "$out" --bun-esm; then
+  compiled=0
+  fail "compile failed for $(basename "$src")"
+elif grep -qi 'deno' "$out"; then
+  fail "legacy runtime reference emitted in $(basename "$out")"
+  grep -in 'deno' "$out" | head -4 | sed 's/^/    /' >&2
+fi
+
+if [ "$compiled" = 1 ]; then
+  # 2. The emitted module must be syntactically valid Bun/JS.
+  if ! bun --check "$out"; then
+    fail "bun --check rejected $(basename "$out")"
+  fi
+
+  # 3. Emission must be byte-for-byte reproducible.
+  second="$TEST_DIR/reproducibility.bun.js"
+  if "${COMPILE_CMD[@]}" "$src" -o "$second" --bun-esm; then
+    if ! cmp "$out" "$second"; then
+      fail "Bun-ESM emission is not reproducible ($(basename "$out") vs $(basename "$second"))"
+    fi
+  else
+    fail "reproducibility recompile failed for $(basename "$src")"
+  fi
 fi
-bun --check "$out"
-second="$TEST_DIR/reproducibility.bun.js"
-"${COMPILE_CMD[@]}" "$src" -o "$second" --bun-esm
-cmp "$out" "$second"
 
+# 4. The retired --deno-esm flag must be rejected with its explanation.
 removed_log="$TEST_DIR/deno-removed.log"
-if "${COMPILE_CMD[@]}" "$src" -o "$out" --deno-esm \
-    >"$removed_log" 2>&1; then
-  echo "error: retired --deno-esm compiled successfully" >&2
-  exit 1
+if "${COMPILE_CMD[@]}" "$src" -o "$out" --deno-esm >"$removed_log" 2>&1; then
+  fail "retired --deno-esm compiled successfully"
+elif ! grep -q 'Deno-ESM was removed' "$removed_log"; then
+  fail "retired --deno-esm rejection lacks 'Deno-ESM was removed'"
 fi
-grep -q 'Deno-ESM was removed' "$removed_log"
 
+# 5. The retired .deno.js output extension must be rejected as E0826.
 removed_json="$TEST_DIR/deno-removed.json"
-if "${COMPILE_CMD[@]}" "$src" -o "${out%.bun.js}.deno.js" --json \
-    >"$removed_json" 2>&1; then
-  echo "error: retired .deno.js output compiled successfully" >&2
-  exit 1
+if "${COMPILE_CMD[@]}" "$src" -o "${out%.bun.js}.deno.js" --json >"$removed_json" 2>&1; then
+  fail "retired .deno.js output compiled successfully"
+else
+  grep -q '"code":"E0826"' "$removed_json" ||
+    fail "retired .deno.js rejection lacks error code E0826"
+  grep -q '"success":false' "$removed_json" ||
+    fail "retired .deno.js rejection lacks success:false"
 fi
-grep -q '"code":"E0826"' "$removed_json"
-grep -q '"success":false' "$removed_json"
 
+# 6. Native Bun harnesses.
+harness_total=0
 for js in "$TEST_DIR"/*.harness.mjs; do
-  (cd "$TEST_DIR" && AFFINESCRIPT_BUN_PROBE=estate bun "$(basename "$js")" alpha beta)
+  name="$(basename "$js")"
+  harness_total=$((harness_total + 1))
+  if ! (cd "$TEST_DIR" && AFFINESCRIPT_BUN_PROBE=estate bun "$name" alpha beta); then
+    fail "bun harness failed: $name"
+  fi
 done
 
+# 7. Unsupported host operations must not compile.
 if "${COMPILE_CMD[@]}" "$TEST_DIR/unsupported_host.affine" \
     -o "$TEST_DIR/unsupported_host.bun.js" --bun-esm; then
-  echo "error: unsupported Bun host operation compiled successfully" >&2
+  fail "unsupported Bun host operation compiled successfully"
+fi
+
+if [ "${#failures[@]}" -gt 0 ]; then
+  echo ""
+  echo "✗ ${#failures[@]} native Bun-ESM check(s) failed:"
+  printf '  - %s\n' "${failures[@]}"
   exit 1
 fi
 
-echo "All native Bun-ESM tests passed."
+echo ""
+echo "All native Bun-ESM tests passed ($harness_total harnesses)."
@@ -4,10 +4,15 @@
 #
 # Directory name `tests/codegen-deno/` is historical. Every fixture is
 # compiled with `--bun-esm` to FILE.bun.js. Harnesses still run under
-# `node` in CI (Node 20 is provisioned; these fixtures do not need the
-# Bun binary — they mock host objects). Native Bun acceptance lives in
-# tools/run_codegen_bun_tests.sh.
-set -euo pipefail
+# `node` in CI (Node 20 is provisioned; fixtures that need a host stub must
+# stub the *Bun* host surface — process.getBuiltinModule / process.argv /
+# process.exit — because that is what the emitted prelude actually reads;
+# a `globalThis.Deno` stub is inert under this backend).
+#
+# Deliberately NOT `set -e`: failures are collected so one broken harness
+# cannot hide every harness after it (the same masking bug that hid 33
+# tests/codegen harnesses; see tools/run_codegen_wasm_tests.sh).
+set -uo pipefail
 
 ROOT_DIR="$(cd "$(dirname "$0")/.." && pwd)"
 TEST_DIR="$ROOT_DIR/tests/codegen-deno"
@@ -22,17 +27,43 @@ fi
 
 echo "Using compiler: ${COMPILE_CMD[*]}"
 
+compile_failures=()
 for src in "$TEST_DIR"/*.affine; do
   out="${src%.affine}.bun.js"
   echo "Compiling $(basename "$src") -> $(basename "$out")"
-  "${COMPILE_CMD[@]}" "$src" -o "$out" --bun-esm
+  if ! "${COMPILE_CMD[@]}" "$src" -o "$out" --bun-esm; then
+    compile_failures+=("$(basename "$src")")
+  fi
 done
 
+if [ "${#compile_failures[@]}" -gt 0 ]; then
+  echo ""
+  echo "::error::${#compile_failures[@]} Bun-ESM fixture(s) failed to compile"
+  printf '  - %s\n' "${compile_failures[@]}"
+  exit 1
+fi
+
 echo ""
 echo "Running ESM harnesses (node, Bun-ESM artefacts)"
+harness_total=0
+harness_failures=()
 for js in "$TEST_DIR"/*.harness.mjs; do
-  echo "node $(basename "$js")"
-  (cd "$TEST_DIR" && node "$(basename "$js")")
+  name="$(basename "$js")"
+  harness_total=$((harness_total + 1))
+  echo "node $name"
+  if ! (cd "$TEST_DIR" && node "$name"); then
+    echo "::error file=tests/codegen-deno/$name::ESM harness failed"
+    harness_failures+=("$name")
+  fi
 done
 
-echo "All codegen Bun-ESM (legacy codegen-deno corpus) tests passed."
+if [ "${#harness_failures[@]}" -gt 0 ]; then
+  echo ""
+  echo "::error::${#harness_failures[@]} of $harness_total Bun-ESM harness(es) failed"
+  echo "Failed harnesses (full output above):"
+  printf '  - %s\n' "${harness_failures[@]}"
+  exit 1
+fi
+
+echo ""
+echo "All codegen Bun-ESM (legacy codegen-deno corpus) tests passed ($harness_total harnesses)."